1. Field of the Invention
The present invention relates to an ink-jet recording apparatus. More particularly, the invention relates to an improved ink-jet recording apparatus that can keep supplying bubble-free ink to the recording head.
2. Description of the Related Art
Ink-jet recording apparatuses have a print head having nozzles, through which ink is ejected when a signal is input from a computer, thereby recording characters and/or images on a recording medium. Any ink-jet recording apparatus is composed, mainly of a recording head unit, an ink tank, and an ink-supplying tube. The recording head unit ejects ink, recording images. The ink tank contains ink to be supplied to the recording head unit. The ink-supplying tube connects the ink tank to the recording head unit.
Ink-jet recording apparatuses thus configured are classified into two types. In one type, the ink tank is replaced by a new one when it becomes empty, whereas the recording head is not replaced at all. In the other type, the recording head and the ink tank are integrally formed, and not only the ink tank but also the recording head is replaced with a new one when the ink tank becomes empty.
In the first-mentioned type, the joint unit, to which the ink tank is attached, is exposed to air when the ink tank is detached from it. Consequently, bubbles enter the ink passage that extends from the ink tank to the recording head. If the bubbles move into the nozzles of the recording head, the ink will be, most probably, not ejected well.
An ink jet recording apparatus designed to solve this problem is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-48492. This apparatus has a deaeration unit for deaerating the ink passage that extends from the ink tank to the recording head.
The ink-jet recording apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-48492 is composed, mainly of a main tank, a deaerator, a relay tank, a recording head, and a tube. The main tank can be replenished with ink. The tube connects the deaerator, relay tank and recording head to the main tank through valves. The deaerator comprises a tank, an ultrasonic transducer, and a vacuum pump. The tank has an ink inlet port through which ink may flow from the main tank and an ink-outlet port through which ink may flow into the relay tank. The ultrasonic transducer is provided on the bottom of the tank. The vacuum pump communicates with the upper part of the tank.
In the ink-jet recording apparatus thus configured, ink flows into the tank through the ink inlet port. Vibrated at high frequency by the ultrasonic transducer, the ink undergoes cavitation. At this point, the vacuum pump is driven. The bubbles are thereby removed from the ink and expelled from the tank. Thus, the ink is deaerated. The ink deaerated is supplied through the ink outlet port or through the relay tank to the recording head. The recording head can therefore print data.